Here's a place where I can post my thoughts on new papers, provide updates on my projects, and post info that will eventually be on my website The Theropod Database - http://theropoddatabase.com/ . It will center on theropods, but may delve into other topics as well such as phylogenetics.

Thursday, March 12, 2020

Oculudentavis is not a theropod

Hi all. This week we got the announcement of a tiny theropod skull in Myanmar amber, which was bound to happen eventually as amazing finds from that deposit keep being published. Alas, whatever Oculudentavis is, it's not a theropod.

Oculudentavis skull (after Xing et al., 2020).

Just look at it. No antorbital fenestra, incomplete ventral bar to the laterotemporal fenestra, huge posttemporal fenestrae, teeth that extend posteriorly far under the orbit...

All of which might be coincidental, but then look at the mandible.

Oculudentavis mandible (after Xing et al., 2020).

That spike-like coronoid process is classic lepidosaur, plus the dentary is way too long compared to the post-dentary elements, then the description says "The tooth geometry appears to be acrodont to pleurodont; no grooves or sockets are discernable." And of course "the scleral ring is very large and is formed by elongated spoon-shaped ossicles; a morphology similar to this is otherwise known only in lizards (for example, Lacerta viridis)."

Add to this the size of this partially fused specimen being smaller than any extant bird (14 mm), and no feather remains, and why is this a theropod again? The endocast is big, but why not a clade of brainier lizards or late surviving megalancosaurs by the Cenomanian?

The authors add it to Jingmai's bird analysis where it ends in a huge polytomy closer to Aves than Archaeopteryx, but outside fake Ornithuromorpha. That's often what happens when a taxon is wrongly placed in a clade. Note the figured placement between Archaeopteryx and Jeholornis is only found using implied weights. At least add it to e.g. Nesbitt's or Ezcurra's archosauromorph analyses, or Cau's theropod analyses before assuming it's a bird.

Thanks to Ruben Molina Perez for suggesting this issue in the first place.

15 comments:

So I'm not alone in this thought. I was going to post a comment but thought I'd hold off for a bit. To your observations I'd add pleurodont teeth, a deep anterior end of the jugal, and a tiny dorsoventrally shallow lacrimal.Also looks very like there was imbricating squamation surrounding the eye (based on close up of the left orbit in the extended data).I see Dave Peters is also pushing the line that it isn't a dinosaur so we are in some illustrious company!

Oh, I see you'd already mentioned the dentition, I missed that when i skimmed your post. The more I think about the more convinced I am that this is some really wierd lepidosauromorph, which is perhaps even more exciting for it might signify a really deep branch that we had no idea existed.

Well, this wouldn't be the first time something like this had happened. "Fulengia" was originally described in Nature as a new lizard (Carroll & Galton 1977), but later turned out to be a dinosaur (Evans & Milner 1989).

Psssst! Secret: the quality of a paper doesn't depend on the journal at all, it depends on the quality of the peer review. If an editor happens to pick only unqualified reviewers – perhaps because none of the qualified ones happened to have time –, blunders happen.

I still haven't read the paper, only skimmed it far enough to confirm that the name is a blunder. First, oculo-, not oculu-; second, Ra should become -rae, not -raae.

Yeah, I know that, of course (viz, what you say about journals and peer review). I have to say - for what it's worth - that the last 'Nature family' paper I published honestly did go through an impressive and very thorough round of checking and double-checking.

My same suspect: https://theropoda.blogspot.com/2020/03/dubbi-sullo-stato-dinosauriano-e-aviano.htmlI also add the presence of a lateral conch on the quadrate (based on 3D model of skull) as a squamate-like feature.Also, I suspect that it is not necessary to suspect some "big-brained" new taxon, but just a very immature ontogenetic stage resulting in proportionally inflated braincase and orbits. Also, based on the 3D model, it seems the snout is dorsoventrally compressed.I also tested its possible squamate placement using the matrix of Gauthier et al. 2012...